Spectroscopic analysis of poly(bisphenol A carbonate) using high resolution C and H NMR

Quantitative structural and end-group analysis of poly(bisphenol A carbonate) (BPA-PC) was carried out and number average molecular weights (M_n) were determined using 125.76 MHz ¹³C and 500.13 MHz ¹H nuclear magnetic resonance (NMR) spectroscopy. BPA-PC with a wide range of end-group ratios (0.26-2.83) and number average molecular weights (1500-9000 g/mol) was synthesized using melt transesterification by changing the initial monomer (bisphenol A and diphenyl carbonate) ratios and reaction conditions. Results of the NMR analysis for the melt-polymerized samples were compared with those of a commercial BPA-PC with a M_n of 16,000 g/mol. It was demonstrated that NMR spectroscopy is a very selective and accurate method not only for quantification of both phenolic and phenyl chain end-groups but also in the structural analysis of main chain groups. Extremely small concentrations of end-groups (∼0.02 per repeating unit) were analyzed. In addition, NMR spectroscopy was found to be an excellent tool for detecting residual monomer and the presence of the reaction byproduct (phenol). The molecular weights that were determined using NMR end-group quantification agreed well with the molecular weights measured by gel-permeation chromatography (GPC).